Abstract: CO₂ mineralization as a promising CO₂ mitigation strategy can employ industrial alkaline solid wastes to achieve net emission reduction of atmospheric CO₂. The red mud is a strong alkalinity waste residue produced from the aluminum industry by the Bayer process which has the potential for the industrial CO₂ large scale treatment. However, limited by complex components of red mud and harsh operating conditions, it is challenging to directly mineralize CO₂ using red mud to recover carbon and sodium resources and to produce mineralized products simultaneously with high economic value efficiently. Herein, we propose a novel electrochemical CO₂ mineralization strategy for red mud treatment driven by hydrogen-cycled membrane electrolysis, realizing mineralization of CO₂ efficiently and recovery of carbon and sodium resources with economic value. The system utilizes H₂ as the redox-active proton carrier to drive the cathode and anode to generate OH^- and H⁺ at low voltage, respectively. The H⁺ plays as a neutralizer for the alkalinity of red mud and the OH^- is used to mineralize CO₂ into generate high-purity NaHCO₃ product. We verify that the system can effectively recover carbon and sodium resources in red mud treatment process, which shows that the average electrolysis efficiency is 95.3% with high-purity (99.4%) NaHCO₃ product obtained. The low electrolysis voltage of 0.453 V is achieved at 10 mA·cm^-2 in this system indicates a potential low energy consumption industrial process. Further, we successfully demonstrate that this process has the ability of direct efficient mineralization of flue gas CO₂ (15% volume) without extra capturing, being a novel potential strategy for carbon neutralization.

Key words: CO₂ mineralization, Red mud, Electrolysis, Waste treatment, Flue gas

摘要： CO₂ mineralization as a promising CO₂ mitigation strategy can employ industrial alkaline solid wastes to achieve net emission reduction of atmospheric CO₂. The red mud is a strong alkalinity waste residue produced from the aluminum industry by the Bayer process which has the potential for the industrial CO₂ large scale treatment. However, limited by complex components of red mud and harsh operating conditions, it is challenging to directly mineralize CO₂ using red mud to recover carbon and sodium resources and to produce mineralized products simultaneously with high economic value efficiently. Herein, we propose a novel electrochemical CO₂ mineralization strategy for red mud treatment driven by hydrogen-cycled membrane electrolysis, realizing mineralization of CO₂ efficiently and recovery of carbon and sodium resources with economic value. The system utilizes H₂ as the redox-active proton carrier to drive the cathode and anode to generate OH^- and H⁺ at low voltage, respectively. The H⁺ plays as a neutralizer for the alkalinity of red mud and the OH^- is used to mineralize CO₂ into generate high-purity NaHCO₃ product. We verify that the system can effectively recover carbon and sodium resources in red mud treatment process, which shows that the average electrolysis efficiency is 95.3% with high-purity (99.4%) NaHCO₃ product obtained. The low electrolysis voltage of 0.453 V is achieved at 10 mA·cm^-2 in this system indicates a potential low energy consumption industrial process. Further, we successfully demonstrate that this process has the ability of direct efficient mineralization of flue gas CO₂ (15% volume) without extra capturing, being a novel potential strategy for carbon neutralization.

关键词: CO₂ mineralization, Red mud, Electrolysis, Waste treatment, Flue gas